Generating truly random numbers is notoriously difficult. But now, using a quantum system, researchers have managed to create 42 genuinely random numbers. Their discovery is a major breakthrough for cryptography, and could one day enable truly private communication online.

Violating Bell's inequalities

In today's issue of Nature, a group of scientists describe how they generated those 42 numbers by measuring atoms at various locations. Now here's where we get quantum. The researchers created these numbers via, as Valerio Scarani puts it in Nature, "the violation of Bell inequalities." What that means is that the researchers relied on the fact that the movement of entangled quantum particles isn't dependent on what you might call a "list of instructions" within each particle. You can't predict where the hell a particle is going to go based on the properties of the particle itself - or even the properties of its locality. So there would be no way to guess what a particle's state is going to be at any given moment, based on where or how that particle started. It's just random.

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Verifying that the numbers are random

OK, but how do you prove your random number generator is truly creating random numbers? That's even harder than getting those 42 random numbers. According to a release about the Nature study:

Randomness is difficult to prove because it is not readily distinguishable from noise and other uncontrollable factors. Antonio Acín and colleagues show that the non-local correlations of entangled quantum particles can be used to certify the presence of genuine randomness. It is thereby possible to design a cryptographically secure random number generator that does not require any assumption about the internal working of the device. They then perform a proof-of-concept experiment in a system of two entangled atoms in which 42 new random numbers are generated.

In this way, Acín and colleagues hope they're on the way to creating a "black box" that spits out provably random numbers, even if you can't look into the box itself.

What's in it for you?

Sounds great, but how will random numbers help Bob send a private message online that nobody can read except for his partner in crime Alice? Think of it this way. Bob sends his ultra-private emails to Alice by encrypting them, turning his dark secrets into a code so nobody at Alice's email provider can grab them and start reading. But how does Alice read them? Well, Alice needs a key to unlock the code.

The fact is, your code, no matter how tricky, is really only as strong as your key. If Alice's key is "iwuvbob," it's going to be easy for Eve the spy to decrypt Bob's emails. But if Alice's key is randomly generated by this black box using quantum entanglement . . . well, that key is going to be pretty damn hard for Eve to guess. Especially if it's 128 characters long, or longer.

So that, my privacy-loving friends, is why you need random numbers to send private information online. Today you got just one step closer to foolproof privacy.